An instrumentation amplifier of this kind is known in practice and is used as measuring amplifier for sensors with which process data are measured such as, for instance, pressure, temperature or current strength. A known application is the application of the instrumentation amplifier in the oil industry, where during drilling measuring equipment is inserted in the drill shank and both the measuring instruments and the instrumentation amplifier are exposed to high temperatures. Said temperatures may range from 175-250.degree. C. Under such conditions much is demanded from the specifications and the stability of said specifications of the instrumentation amplifier and consequently from the components incorporated therein. A problem is created by the circumstance that differences in drift between the components of the instrumentation amplifier result in precision and calibration problems; there is another awkward circumstance with the above-mentioned application namely, that it is impossible to carry out maintenance on an instrumentation amplifier inside a drill shank. If such an instrumentation amplifier unexpectedly exhibits problems, the costs involved in replacing it are excessively high in relation to the cost of such an instrumentation amplifier.